The invention relates to a modular control block for use in the field of analytical procedures. The invention is concerned in particular with the constructional design of a control block which may assume a plurality of different control functions, such as for example dosing, distribution, mixing or flushing, or a combination of these control functions, simply by a change in the line-up of the individual modules.
Such control blocks in modular designxe2x80x94in each case equipped with valvesxe2x80x94are already successfully in use in other areas of control engineering, such as in pneumatic applications. Assembled as a combination of modular units, they provide very great flexibility and, the parts also being standardised, cost-effective production and warehousing is achieved.
So far there was no standardisation in the field of analytical procedures, as regards the interconnection of the valves and the components used, on account of the great variety of applications and of the complex ways of combination, as well as the high requirements exacted with respect to chemical resistance, reduced lost space, reduced gaps and internal volume.
Control blocks for applications in the field of analytical procedures are conventionally produced in such a way that a number of valves are so interconnected as to obtain the desired functions. To this purpose, mechanically machined control blocks, tailor-made to suit specific requirements, are produced, to which the valves are connected by means of flanges, to give an example. This method gives rise to rigid and cost-intensive control blocks which have to be designed and produced for each and every application requirement.
At a later time, furthermore, it is possible only at high expense in terms of cost and modification time to integrate sensors for the control of the medium, such as for flow measurements, into control blocks produced according to conventional methods. In most cases, sensors are then arranged before or after the control block; this gives rise to an increase of the internal volume and the lost volume.
It has been found to be a disadvantage in conventional control blocks for applications in the field of analytical procedures that for conventional unions between the individual elements of a valve block O-rings are used in preference, where lost space and gaps are not completely avoidable at the joining points.
A better solution is provided by the use of profiled O-rings or special form seals, but these are very expensive.
It is therefore the object of the invention to improve the control blocks for use in the field of analytical procedures in a way that both specific customer requirements may be complied with and that a standardisation of the blocks is realised, which will result in lower production costs because the units can be made in large production batches. Furthermore, and in accordance with the invention, the elements may be modified in such a way that sensors may be installed without lost space or gaps, if required. These sensors may serve, for example, the purpose of determining whether a flow exists in specific channels and of transferring the result to an electronic evaluation processor.
According to the invention, a modular control block for analytical procedures comprising a plurality of individual elements is provided for this purpose, the individual elements each containing at least one channel for the inflow and for the outflow of fluids, and being adapted to be connected to one another at appropriate points of connection, where all the individual elements have the same outer contour and may be arranged in-line or staggered, wherein different functional modes of the control block may be achieved by arranging the individual elements in line, staggered, or in a combined configuration of in-line or staggered individual elements.
The individual components of the modular control block according to the invention have the advantage that the outer shape and the position of the main channels is identical in all elements. In the case of the present invention, individual elements are used which may be combined in a number of different ways. The dimensional pattern of the connecting valves and sensor outputs is designed in such a way that both inflow and outflow ports may be controlled by means of electric bus lines which are normal in pneumatic systems. In a preferred embodiment, the control block is controlled via a multi-pole plug or a field bus.
The arrangement of the elements may be configured in different ways, depending on the application intended. If, for example, the elements are arranged in line without mutual shift, the functions realised mean that the fluids concerned flow within a common channel or are taken from a common channel. In the case of a staggered line-up, however, functions are created where the fluid flows through the elements one after the other. Even a combination of in-line arranged elements with mutually shifted elements is possible. The staggered arrangement is made possible by the fact that the connection bores in the individual elements are at the same height. In the case of the present invention, a plurality of multi-arrangements for the realisation of complex control functions is created by any desired combination of elements arranged in-line and/or staggered.
In a further development of the invention, the at least one channel is formed by a control bore, and the depth of the control bores differs for different individual elements. The position of the control bores, that is of the main channels, is identical for all elements, only the depth of the control bores differs, depending on the function of the element. By taking this measure it becomes possible to produce the individual elements as low-cost injection moulded parts only one die mould has to be produced for all the different embodiments. Modifications are created, for example, by the simple replacement of interchangeable shutters in the die mould.
It is furthermore of advantage that a sensor, for example for flow or temperature measurements, can be incorporated in each individual element produced in accordance with the invention. In order to insert the sensor free of lost space and gaps, each element is provided with one or more conical blind-end bores which become gradually narrower towards the main channel, and which are separated from it by a thin material layer. This thin layer will only be pierced when a sensor is installed.
In the case of the present invention, the sensor is inserted into a sleeve of an elastomer material and, together with it, is pushed into the ruptured conical bore. According to the invention, the conical bore serves the purpose of holding the unit, consisting of sleeve and sensor, in such a way that it is retained self-locking in the housing. The contact pressure of the sleeve is greatest in its frontal area, where the sensor protrudes from the sleeve into the channel, and therefore a jointing seal free of lost space and gaps is achieved for the sensor element. The fluid flows around the sensor. In a preferred embodiment, the area around the connecting electrical leads is filled with casting resin in the interest of electrical safety. In the case of a further embodiment, this area is made safe by means of a clamping element. This prevents the installed sensor from changing position.
In order to enable the modular valve block to be re-equipped with sensors in a simple way at a later date, for example with pressure sensors, the invention provides a special element for sensors which may be re-equipped without any need for modification of the modular control block. Such an element is simply connected to an existing individual element by means of a flange, instead of the connecting nipple. On the basis of the proposed arrangement, even in this case the design and assembly of both the housing and the sensor are such that no lost spaces or gaps are produced, which otherwise may lead to deposits as the area is washed by the fluids.
According to the present invention, transition points without lost space are achieved by the provision of recesses with a tapered bottom to accommodate the sealing elements. This ensures that the sealing elementxe2x80x94preferably a rectangular sealxe2x80x94is subjected to a greater pressure towards the fluid carrying channel than on the side opposed to the fluid flow. In this way a jointing point is created which is hermetically sealed and free of lost space and gaps. There is then no need for expensive form seals; rectangular seals may be made at low cost of almost any sealing material.